Check if a Value exists in a Two-dimensional List in Python

# Check if a Value exists in a Two-dimensional List in Python

Use the any() function to check if a value exists in a two-dimensional list.

The any() function will return True if the value exists in the list and False otherwise.

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my_2d_list = [['one', 'two'], ['three', 'four'], ['five', 'six']]


if any('three' in nested_list for nested_list in my_2d_list):
    # 👇️ This runs
    print('three is contained in the two-dimensional list')
else:
    print('three is NOT contained in the two-dimensional list')

We used a generator expression to iterate over the two-dimensional list.

On each iteration, we check if a specific value is contained in the nested list.

The any function takes an iterable as an argument and returns True if any element in the iterable is truthy.

# Defining a reusable function

If you have to do this often, define a reusable function.

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def is_in_2d_list(two_dimensional_list, value):
    return any(
        value in nested_list
        for nested_list in two_dimensional_list
    )


my_2d_list = [['one', 'two'], ['three', 'four'], ['five', 'six']]

print(is_in_2d_list(my_2d_list, 'one'))  # 👉️ True
print(is_in_2d_list(my_2d_list, 'abc'))  # 👉️ False

if is_in_2d_list(my_2d_list, 'one'):
    print('The value is in the two-dimensional list')
else:
    print('The value is NOT in the two-dimensional list')

The function takes a two-dimensional list and a value as parameters and returns True if the value is contained in the two-dimensional list and false otherwise.

# Getting the nested list that contains the value

You can use the assignment expression syntax if you need to get the nested list that contains the specified value.

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my_2d_list = [['one', 'two'], ['three', 'four'], ['five', 'six']]


if any('three' in (match := nested_list) for nested_list in my_2d_list):
    # 👇️ this runs
    print('three is contained in the two-dimensional list')

    print(match)  # 👉️ ['three', 'four']

    print(match.index('three'))  # 👉️ 0
else:
    print('three is NOT contained in the two-dimensional list')

Assignment expressions allow us to assign to variables within an expression using the NAME := expression syntax.

If the iterable is empty or none of the elements in the iterable are truthy, the any function returns False.

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my_2d_list = [['one', 'two'], ['three', 'four'], ['five', 'six']]


if any('HELLO' in nested_list for nested_list in my_2d_list):
    print('HELLO is contained in the two-dimensional list')
else:
    # 👇️ this runs
    print('HELLO is NOT contained in the two-dimensional list')

None of the nested lists contain an item with the specified value, so the condition is never met and the any() function returns False.

Alternatively, you can use a for loop.

# Check if a Value exists in a Two-dimensional List using a for loop

This is a three-step process:

1. Use a for loop to iterate over the list of lists.
2. Use the in operator to check if each sublist contains the value.
3. Break out of the loop once you find a list that contains the value.

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my_2d_list = [['one', 'two'], ['three', 'four'], ['five', 'six']]

exists_in_list = False

for nested_list in my_2d_list:
    if 'three' in nested_list:
        exists_in_list = True

        print(nested_list)

        break

if exists_in_list:
    print('The value exists in the two-dimensional list')
else:
    print('The value does NOT exist in the two-dimensional list')

We used a for loop to iterate over the two-dimensional list.

On each iteration, we check if the current sublist contains a given value.

If the value is contained in the sublist, we set the exists_in_list variable to True and break out of the loop.

The break statement breaks out of the innermost enclosing for or while loop.

If the value is not contained in the two-dimensional list, the exists_in_list variable remains set to False.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• How to get the length of a 2D Array in Python
• Check if any element in a List matches Regex in Python
• Check if all/any elements in List meet condition in Python
• Check if multiple Values are in a List in Python